Fanconi anemia (FA) is a heterogeneous disease involving multiple organ systems including hematologic, skeletal, renal, neurologic and endocrine. Patients are predisposed to malignancies, particularly acute myelogenous leukemia (AML). Although the genes for two of the eight FA complementation groups (FAC and FAA) have been cloned, and mutations identified in both of these genes in affected individuals, the precise function of these genes has yet to be elucidated. It is the objective of this protocol to define the phenotypic spectrum of this rare syndrome by study of a large number of patients with diverse features. These patients will also provide a source of cells for molecular studies. It is an objective our study to extend our ability to define the FA genotype of all patients and to make genotype-phenotype correlations. This would enable physicians to better predict clinical outcome and aid decision-making regarding major therapeutic modalities for this clinically heterogeneous disorder. Understanding the genetic defect in FA should lead to a better understanding of birth defects and cancer predisposition in general, and the interaction of genetic and epigenetic factors in their pathogenesis.